Intervertebral implant having extendable bone fixation members

ABSTRACT

An intervertebral implant is configured to be fixed in an intervertebral space defined by a first vertebral body and a second vertebral body. The intervertebral implant includes an implant body sized to be inserted into an intervertebral space, and a fixation assembly configured to be attached to the implant body. The fixation assembly includes a housing that defines a first vertebral body facing surface and a second vertebral body facing surface spaced from the first vertebral body facing surface along a transverse direction. The fixation assembly further includes at least one fixation member supported by the housing and movable from a retracted position to an extended position, whereby in the extended position the fixation member extends out from the housing and into one of the vertebral bodies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/243,297 filed Sep. 17, 2009, and further claimsthe benefit of U.S. Provisional Patent Application Ser. No. 61/260,364filed Nov. 11, 2009, the disclosure of each of which is herebyincorporated by reference as if set forth in its entirety herein. Thisapplication is a divisional of U.S. patent application Ser. No.14/064,434 filed Oct. 28, 2013, and issuing Jan. 13, 2015, as U.S. Pat.No. 8,932,359, which is a divisional of U.S. patent application Ser. No.12/884,664 filed Sep. 17, 2010, and issuing Dec. 31, 2013, as U.S. Pat.No. 8,617,245, the disclosure of each of which is hereby incorporated byreference as if set forth in its entirety herein.

BACKGROUND

The human vertebral column (also known as the backbone or spine) housesthe spinal cord in its spinal canal. The vertebral column is made up ofa plurality of vertebrae. A typical vertebra includes two primary parts,including an anterior portion that includes the vertebral body, and aposterior portion that encloses the foramen. Each vertebral body definessuperior and inferior vertebral endplates that, such that adjacentvertebrae define an intervertebral space that includes disc materialbetween the respective endplates.

Historically, spinal abnormalities have indicated complete removal of adisc from the intervertebral space followed by fusion the adjacentvertebrae together. This “spinal fusion” procedure, which is still inuse today, is a widely accepted surgical treatment for symptomaticlumbar and cervical degenerative disc disease. Early fusion proceduresused an implant made of bone from a patient's hip or a cadaver bone as aspacer in the intervertebral space so as to properly position theadjacent vertebrae until the vertebrae were fused together. More modernprocedures use implants made from a material having a relatively lowmodulus of elasticity to encourage bone growth. For instance, theimplant can contain some of the patient's own bone, e.g., withinapertures of the implant. Conventional implants can be made from desiredmaterial, including radiolucent materials such as polyetheretherketone(PEEK), ultra-high molecular weight polyethylenes (UHMWPE) orpolysulfones (PSU). It can be desirable for the material to have amodulus of elasticity between 3 and 5 GPa.

Conventional intervertebral implant designs have attempted to achieveimplant fixation in the intervertebral space.

SUMMARY

In accordance with one embodiment, an intervertebral implant isconfigured to be fixed in an intervertebral space defined by a firstvertebral body and a second vertebral body. The intervertebral implantincludes an implant body sized to be inserted into an intervertebralspace, and a fixation assembly configured to be attached to the implantbody. The fixation assembly includes a housing that defines a firstvertebral body facing surface and a second vertebral body facing surfacespaced from the first vertebral body facing surface along a transversedirection. The housing defines a channel. The fixation assembly furtherincludes a first superior staple and a second inferior staple that istransversely opposite the first superior staple. Each staple issupported in the channel such that each staple includes a crossbar and apair of spaced that extend transversely out from the crossbar. Eachcrossbar defines respective first and second cam surfaces. Theintervertebral implant further includes an actuator that is configuredto translate along a distal direction within the housing that issubstantially orthogonal to the transverse direction. The actuator isconfigured to substantially simultaneously engage the first and secondcam surfaces so as to cause terminal ends of the pins of the firststaple to translate in the transverse direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofexample embodiments of the present disclosure, will be better understoodwhen read in conjunction with the appended drawings. For the purposes ofillustrating the example embodiments of the present disclosure,references to the drawings are made. It should be understood, however,that the application is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1A is a perspective view of a pair of vertebral bodies separated byan intervertebral space;

FIG. 1B is a perspective view of the vertebral bodies illustrated inFIG. 1, and an intervertebral implant inserted into the intervertebralspace between the two vertebral bodies;

FIG. 2A is a perspective view of an intervertebral implant including animplant body and a fixation assembly connected to the intervertebralimplant, showing the fixation assembly in accordance with one embodimentin a retracted position;

FIG. 2B is a perspective view of the intervertebral implant asillustrated in FIG. 2A, showing the fixation assembly in an extendedposition;

FIG. 2C is an exploded assembly view of the intervertebral implantillustrated in FIG. 2A, showing the connection of the fixation assemblyto the implant body;

FIG. 2D is a top plan view of the intervertebral implant illustrated inFIG. 2A having portions removed for the purposes of clarity;

FIG. 2E is a front elevation view of the intervertebral implant asillustrated in FIG. 2A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 2F is a side view of the intervertebral implant as illustrated inFIG. 2E, having portions removed for the purposes of clarity;

FIG. 2G is a perspective view of the fixation assembly as illustrated inFIG. 2B;

FIG. 2H is a top plan view of the intervertebral implant as illustratedin FIG. 2B, having portions removed for the purposes of clarity;

FIG. 2I is a front elevation view of the intervertebral implant asillustrated in FIG. 2B, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 2J is a side view of the intervertebral implant as illustrated inFIG. 2I, having portions removed for the purposes of clarity;

FIG. 3A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 3B is a front elevation view of the intervertebral implant asillustrated in FIG. 3A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 3C is a side elevation view of the intervertebral implant asillustrated in FIG. 3B, having portions removed for the purposes ofclarity;

FIG. 3D is a top plan view of the intervertebral implant illustrated inFIG. 3A, but showing the fixation assembly in an extended position;

FIG. 3E is a front elevation view of the intervertebral implant asillustrated in FIG. 3D, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 3F is a side elevation view of the intervertebral implant asillustrated in FIG. 3D, having portions removed for the purposes ofclarity;

FIG. 3G is a top plan view of an intervertebral implant similar to theintervertebral implant as illustrated in FIG. 3D, but constructed inaccordance with an alternative embodiment;

FIG. 4A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 4B is a front elevation view of the intervertebral implant asillustrated in FIG. 4A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 4C is a side elevation view of the intervertebral implant asillustrated in FIG. 4B, having portions removed for the purposes ofclarity;

FIG. 4D is a top plan view of the intervertebral implant illustrated inFIG. 4A, but showing the fixation assembly in an extended position;

FIG. 4E is a front elevation view of the intervertebral implant asillustrated in FIG. 4D, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 4F is a side elevation view of the intervertebral implant asillustrated in FIG. 4D, having portions removed for the purposes ofclarity;

FIG. 4G is a top plan view of an intervertebral implant similar to theintervertebral implant as illustrated in FIG. 4D, but constructed inaccordance with an alternative embodiment;

FIG. 5A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 5B is a front elevation view of the intervertebral implant asillustrated in FIG. 5A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 5C is a side elevation view of the intervertebral implant asillustrated in FIG. 5B, having portions removed for the purposes ofclarity;

FIG. 5D is a top plan view of the intervertebral implant illustrated inFIG. 5A, but showing the fixation assembly in an extended position;

FIG. 5E is a front elevation view of the intervertebral implant asillustrated in FIG. 5D, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 5F is a side elevation view of the intervertebral implant asillustrated in FIG. 5D, having portions removed for the purposes ofclarity;

FIG. 5G is a top plan view of an intervertebral implant similar to theintervertebral implant as illustrated in FIG. 5D, but constructed inaccordance with an alternative embodiment;

FIG. 6A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in an extended position;

FIG. 6B is a front elevation view of the intervertebral implant asillustrated in FIG. 6A, shown disposed in an intervertebral space and ina retracted position;

FIG. 6C is a front elevation vie of the intervertebral implant asillustrated in FIG. 6B, having portions removed for the purposes ofclarity;

FIG. 6D is a side elevation view of the intervertebral implant asillustrated in FIG. 6C, having portions removed for the purposes ofclarity;

FIG. 6E is a front elevation view of the intervertebral implant asillustrated in FIG. 6A, having portions removed for the purposes ofclarity, showing the fixation assembly in an extended position;

FIG. 6F is a side elevation view of the intervertebral implant asillustrated in FIG. 6E, having portions removed for the purposes ofclarity;

FIG. 6G is a side elevation view of an extractor of the intervertebralimplant illustrated in FIG. 6A, configured to iterate the fixationassembly to the retracted position;

FIG. 6H is a top plan view of the extractor illustrated in FIG. 6G;

FIG. 6I is a side elevation view of the implant as illustrated in FIG.6A, showing the extractor installed with the fixation assembly in anextended position, having portions removed for the purposes of clarity;

FIG. 6J is a front elevation view of the intervertebral implant asillustrated in FIG. 6I, having portions removed for the purposes ofclarity;

FIG. 6K is a front elevation view of the intervertebral implant asillustrated in FIG. 6I, showing an actuator of the fixation assembly,and showing the fixation assembly in a retracted position;

FIG. 6L is a front elevation view of the intervertebral implant asillustrated in FIG. 6K, but showing portions removed for the purposes ofclarity;

FIG. 6M is a side elevation view of the intervertebral implant asillustrated in FIG. 6L, showing portions removed for the purposes ofclarity;

FIG. 6N is a top plan view of the intervertebral implant as illustratedin FIG. 6M, showing portions removed for the purposes of clarity;

FIG. 7A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 7B is a front elevation view of the intervertebral implant asillustrated in FIG. 7A, showing portions removed for the purposes ofclarity, disposed in an intervertebral space;

FIG. 7C is a side elevation view of the intervertebral implant asillustrated in FIG. 7B, showing portions removed for the purposes ofclarity;

FIG. 7D is a top plan view of the intervertebral implant illustrated inFIG. 7A, showing the fixation assembly in an extended position;

FIG. 7E is a front elevation view of the intervertebral implant asillustrated in FIG. 7D, showing portions removed for the purposes ofclarity, disposed in an intervertebral space;

FIG. 7F is a side elevation view of the intervertebral implant asillustrated in FIG. 7E, showing portions removed for the purposes ofclarity;

FIG. 8A is a side elevation view of an intervertebral implant similar tothe intervertebral implant illustrated in FIG. 7A, but constructed inaccordance with an alternative embodiment, having portions removed forthe purposes of clarity;

FIG. 8B is a front elevation view of the intervertebral implantillustrated in FIG. 8A;

FIG. 9A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 9B is a front elevation view of the intervertebral implant asillustrated in FIG. 9A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 9C is a front elevation view of the intervertebral implantillustrated in FIG. 9B, having portions removed for the purposes ofclarity, showing the fixation assembly in an extended position;

FIG. 9D is a front elevation view of an intervertebral implant similarto that illustrated in FIG. 9B, but showing a bone fixation member ofthe fixation assembly constructed in accordance with an alternativeembodiment;

FIG. 9E is a front elevation view of the intervertebral implant asillustrated in FIG. 9D, showing the fixation assembly in an extendedposition;

FIG. 10A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 10B is a front elevation view of the intervertebral implantillustrated in FIG. 10A, having portions removed for the purposes ofclarity, shown in an intervertebral space, and showing the fixationassembly in a retracted position;

FIG. 10C is a front elevation view of the intervertebral implant asillustrated in FIG. 10B, but showing the fixation assembly in anextended position;

FIG. 11A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 11B is a front elevation view of the intervertebral implantillustrated in FIG. 11A, having portions removed for the purposes ofclarity, shown in an intervertebral space, and showing the fixationassembly in a retracted position;

FIG. 11C is a front elevation view of the intervertebral implant asillustrated in FIG. 11B, but showing the fixation assembly in anextended position;

FIG. 11D is a front elevation view of the intervertebral implantillustrated in FIG. 11B, showing the intervertebral implant in anas-assembled position;

FIG. 11E is a front elevation view of the intervertebral implantillustrated in FIG. 11B, showing the intervertebral implant in anas-supplied position;

FIG. 11F is a top plan view of the intervertebral implant as illustratedin FIG. 11E;

FIG. 12A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 12B is a front elevation view of the intervertebral implant asillustrated in FIG. 12A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 12C is a front elevation view of the intervertebral implant asillustrated in FIG. 12B, but showing the fixation assembly in anextended position;

FIG. 13A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 13B is a front elevation view of the intervertebral implant asillustrated in FIG. 13A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 13C is a side elevation view of the intervertebral implant asillustrated in FIG. 13B, having portions removed for the purposes ofclarity;

FIG. 13D is a front elevation view of the intervertebral implant asillustrated in FIG. 13B, showing the fixation assembly in an extendedposition;

FIG. 13E is a side elevation view of the intervertebral implant asillustrated in FIG. 13D, having portions removed for the purposes ofclarity;

FIG. 13F is a schematic top plan view of an intervertebral implantsimilar to the intervertebral implant as illustrated in FIG. 13A, butconstructed in accordance with an alternative embodiment;

FIG. 14A is a top plan view of an intervertebral implant including animplant body and a fixation assembly constructed in accordance with analternative embodiment, having portions removed for the purposes ofclarity, showing the fixation assembly in a retracted position;

FIG. 14B is a front elevation view of the intervertebral implant asillustrated in FIG. 14A, having portions removed for the purposes ofclarity, shown in an intervertebral space;

FIG. 14C is a front elevation view of the intervertebral implant asillustrated in FIG. 14B, showing the fixation assembly in an extendedposition;

DETAILED DESCRIPTION

Referring to FIGS. 1A-B, a first superior vertebral body 12 a defines asuperior vertebral endplate 13 a of an intervertebral space 14, and anadjacent second inferior vertebral body 12 b defines an inferiorvertebral endplate 13 b of the intervertebral space 14. Thus, theintervertebral space 14 is disposed between the vertebral bodies 12 a-b.The vertebral bodies 12 a-b can be anatomically adjacent vertebralbodies, or can remain after a discectomy has been performed that removeda vertebral body from a location between the vertebral bodies 12 a-b. Asillustrated, the intervertebral space 14 is illustrated after adiscectomy, whereby the disc material has been removed to prepare theintervertebral space 14 to receive an orthopedic implant, such as theintervertebral implant 10 illustrated in FIG. 2. Thus, the implant 10 isconfigured to be inserted into the intervertebral space 14, and achieverestoration of height while maintaining mobility. The intervertebralspace 14 can be disposed anywhere along the spine as desired. As will beappreciated from the description below, the implant 10 can be sized asdesired so as to be implantable in an intervertebral disc space in anyregion of the spine, including the lumbar region, thoracic region,cervical region, sacral region, and coccygeal region.

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inner” or “distal” and “outer” or “proximal” refer to directionstoward and away from, respectively, the geometric center of the implantand related parts thereof. The words, “anterior”, “posterior,”“superior,” “inferior,” “medial,” “lateral,” and related words and/orphrases designate preferred positions and orientations in the human bodyto which reference is made and are not meant to be limiting. Theterminology includes the above-listed words, derivatives thereof andwords of similar import.

The implant 10 and various components of the implant 10 are describedherein extending horizontally along a longitudinal direction L and alateral direction A, and vertically along a transverse direction T.Unless otherwise specified herein, the terms “lateral,” “longitudinal,”and “transverse” are used to describe the orthogonal directionalcomponents of various components. The lateral direction A andlongitudinal direction L are angularly offset, for instancesubstantially orthogonal, with respect to each other and with respect tothe transverse direction T. It should be appreciated that while thelongitudinal and lateral directions are illustrated as extending along ahorizontal plane, and that the transverse direction is illustrated asextending along a vertical plane, the planes that encompass the variousdirections may differ during use. For instance, when the implant 10 isimplanted into an intervertebral space, such as the intervertebral space14, the transverse direction T extends generally along thesuperior-inferior (or cranial-caudal) direction, while the plane definedby the longitudinal direction L and lateral direction A lie generally inthe anatomical plane defined by the anterior-posterior direction, andthe medial-lateral direction, respectively. Accordingly, the directionalterms “vertical” and “horizontal” are used to describe the implant 10and its components as illustrated merely for the purposes of clarity andillustration.

Referring now to FIGS. 2A-C, the intervertebral implant 10 includes animplant body 20 and a fixation assembly 22 configured to secure theimplant body 20 to the first and second vertebral bodies 12 a and 12 bin the intervertebral space 14. The implant 10 and components thereofcan be formed from any of a variety of biocompatible materials, such ascobalt chromium molybdenum (CoCrMo), titanium and titanium alloys,stainless steel, ceramics, or polymers such as polyetheretherketone(PEEK), ultra-high molecular weight polyethylenes (UHMWPE) orpolysulfones (PSU), bioresorbable materials, and bonegraft (for exampleallograft and xenograft). A coating may be added or applied to theimplant 10 to improve physical or chemical properties. The coatings mayhelp to ensure bony in or on growth or medication. Examples of coatingsinclude plasma-sprayed titanium coating or hydroxyapatite.

The implant body 20 defines a front end 24 and a longitudinally opposedrear end 26, a top end 28 and a transversely opposed bottom end 30, andopposed lateral sides 32 and 34. The top and bottom ends 28 and 30 canbe configured to face the corresponding vertebral endplates 13 a and 13b of the superior and inferior vertebral bodies 12 a and 12 b,respectively. In some embodiments, the top and bottom ends 28 and 30 canbe configured to abut the corresponding vertebral endplates 13 a and 13b. The implant 10 can be inserted into the intervertebral space 14 alongan insertion direction which can be an anterior-posterior approach (forinstance when the vertebral bodies 12 a and 12 b are cervical vertebralbodies) in an orientation such that the front longitudinal end 24 isanterior to the rear longitudinal end 26.

The implant body can be sized and shaped as desired, and is illustratedas substantially “D” shaped, such that the front end 24 extendssubstantially straight in the lateral direction A, and the lateral sides32 and 34 curve toward each other in a rearward direction to the rearend 26. In accordance with the illustrated embodiment, the implant body20 defines a substantially central “D” shaped central opening 25 thatextends transversely into (through as illustrated) the implant body 20.The central opening 25 can receive any suitable bone growth promotingmaterial, such as allograft and xenograft to promote bone growth withthe vertebral bodies 12 a-b after implantation of the implant 10 intothe intervertebral space 14. The implant body 20 can be solid asillustrated, or can define perforations that extend into or through theimplant body 20 that can, for instance, receive the bone growthpromoting material.

The implant body 20 defines a transverse height H between the top andbottom ends 28 and 30. The height H can be substantially constant fromthe front end 24 to the rear end 26, or can be variable from the frontend 24 to the rear end 26 so as to impart or restore a lordoticcurvature to the vertebral bodies 12 a and 12 b. Thus, the height H candecrease in a rearward direction from the front end 24 toward the rearend 26, or can increase in the rearward direction. Furthermore, theheight H can be constant or variable between the lateral sides 32 and 34as desired. In this regard the top and bottom ends 28 and 30 can besubstantially planar, or can be curved, undulated, or otherwise shapedas desired so as to correspond to the vertebral endplates 13 a and 13 b.A kit of implants 10 can also be provided, each having a plurality ofimplant bodies 20 of different shapes or sizes. For instance, the kitcan include a plurality of implant bodies 20 of different heights H,such that at least one of the implant bodies 20 in the kit cancorrespond with the corresponding different height of intervertebralspaces along the vertebral column of a given patient, or of anintervertebral space of different patients.

The fixation assembly 22 includes a fixation housing 36 that isconfigured to be mounted or otherwise connected to the implant body 20.The fixation housing 36 supports, either directly or indirectly, atleast one bone or vertebral fixation member 38 and at least one actuator40 that is configured to iterate the fixation assembly 22, andparticular the at least one fixation member 38, between a retractedposition illustrated in FIG. 2A and an extended position illustrated inFIG. 2B so as to fix the fixation assembly 22 and thus the implant 10 tothe vertebral bodies 12 a and 12 b. The fixation housing 36 defines afront end 42 and a longitudinally opposed rear end 44, a top end 46 anda transversely opposed bottom end 48, and opposed lateral side 50 and52. The top and bottom ends 46 and 48 can be configured to face thecorresponding vertebral endplates 13 a and 13 b of the superior andinferior vertebral bodies 12 a and 12 b, respectively. In someembodiments, the top and bottom ends 46 and 48 can be configured to abutthe corresponding vertebral endplates 13 a and 13 b. In accordance withthe illustrated embodiment, the front end 42 defines a proximal end ofthe fixation housing 36, and the rear end 44 defines a distal end of thefixation housing 36 that is spaced from the proximal end in theinsertion direction along a central longitudinal axis 37.

The fixation housing 36 and the implant body 20 include respectivecomplementary engagement members 54 and 56 that can be configured asdesired to mount or otherwise connect the fixation housing 36 to theimplant body 20. In accordance with the illustrated embodiment, theengagement member 54 of the fixation assembly 22 is configured as atransversely elongate rail 58 that projects laterally out from the sides50 and 52 of the fixation housing 36. The rails 58 can terminate abovethe bottom end 48 of the fixation housing 36. In accordance with theillustrated embodiment, the complementary engagement member 56 of theimplant body 20 is configured as a pair of transversely elongate slots60 sized to receive the rails 58. The slot 60 can terminate above thebottom end 30 of the implant body 20. The slots 60 are disposed onopposed sides of a pocket 62 that is defined by the implant body 20 andsized to receive the fixation housing 36.

Accordingly, the fixation assembly 22 can be can be connected to theimplant body 20 by inserting the fixation housing 36 into the pocket 62of the implant body 20 such that the rails 58 are received in the slots60. The fixation housing 36 can define a longitudinal length greaterthan the front end 24 of the implant body 20, such that the fixationhousing 36 extends longitudinally into the central opening 25. The rails58 and slots 60 can be sized such that the top and bottom ends 46 and 48of the fixation housing 36 are substantially aligned or flush with thetop and bottom ends 28 and 30 of the implant body 20. Accordingly, thetop and bottom ends 46 and 48 of the fixation housing 36, and the topand bottom ends 28 and 30 of the implant body 20, can be configured toabut the vertebral endplates 13 a and 13 b. Alternatively, part or allof the top and bottom ends 28 and 30 of the implant body 20 and/or thetop and bottom ends 46 and 48 of the fixation housing can be recessedwith respect to the vertebral endplates 13 a and 13 b. Whether the topends 28 and 46 and bottom ends 30 and 48 abut or are recessed from therespective vertebral endplates 13 a and 13 b, they can face a directionhaving a transverse directional component, such that it can be said thatthe top ends 28 and 46 and bottom ends 30 and 48 face the vertebralbodies 12 a and 12 b and thus define vertebral body facing surfaces. Asdescribed above, the engagement members 54 and 56 can be configured asdesired to facilitation the connection of the fixation assembly 20 tothe implant body 20. For instance, the fixation assembly 22 can beintegral with the implant body 20.

Referring also to FIGS. 2D-F, the fixation assembly 22 includes at leastone aperture 63 defined by the fixation housing 36 that receives theactuator 40 and at least one channel that receives the at least onefixation member 38. In accordance with the illustrated embodiment, thefixation housing 36 defines a first pair of laterally spaced superiorchannels 64 and a second pair of laterally spaced inferior channels 65that can be vertically aligned with the superior channels 64. Thechannels 64 and 65 can extend in any direction as desired, and extend ina direction having both longitudinal and transverse directionalcomponents in accordance with the illustrated embodiment. For instancethe superior channels 64 extend longitudinally and transversely upwardsso as to define a first proximal end that extends from the proximal end42 of the fixation housing 36 to a second distal end that extends to thetop end 46. The inferior channels 65 extend longitudinally andtransversely down so as to define a first proximal end that extends fromthe proximal end 42 of the fixation housing 36 to the distal end thatextends to the bottom end 48. The distal ends of the channels 64 and 65are thus transversely and longitudinally displaced with respect to therespective proximal ends of the channels 64 and 65.

In accordance with the illustrated embodiment, the channels 64 and 65extend laterally into the sides 50 and 52 of the fixation housing 36,though they can be alternatively positioned as desired. The fixationassembly 22 can include a pair of cover plates 66 that are attached tothe sides 50 and 52 of the fixation housing 36 so as to laterally coverand laterally close the channels 64 and 65. Thus, the cover plates 66can include the engagement rails 58 as described above.

The fixation member 38 can be provided as a first staple 68 that definesa proximal end 77 and an opposed distal or terminal end 79 that, inturn, defines a corresponding tip 73 that is configured to be insertedinto a corresponding vertebral body (e.g., through the endplate) so asto fix the fixation assembly 22 and thus the implant 10 to the vertebralbody. The staple 68 includes a bass in the form of a crossbar 70 at theproximal end 77 and at least a first pair of laterally spaced pins 72that extend out from the crossbar 70 at any location, such as at opposedouter ends of the crossbar 70 as illustrated. The implant 10 can includea second fixation member provided as a second staple 69 can furtherinclude a second pair of laterally spaced pins 74 that extend out from asecond crossbar 71 at any location, such as at opposed outer ends of thecrossbar 71 as illustrated.

The pins 72 and 74 are attached to the respective crossbars 70 and 75 attheir proximal ends, and define the tips 73 at their distal ends. Whenthe staples 68 and 69 are in the recessed position, the pins 72 and 74can be entirely recessed in the fixation housing 36 such that the tips73 do not extend out from the fixation housing 36. The tips 73 of thefirst and second pairs of pins 72 and 74 can extend into the vertebralbodies 12 a and 12 b when the fixation member 38 is in the extendedposition. Thus the implant 10 can include a pair of fixation membersthat define respective pairs of pins 72 and 74, the first pair of pins72 defining a tip 73 at its distal or terminal end that is configured toextend into the first vertebral body 12 a in the extended position, andthe second pair of pins 72 defining a tip that is configured to extendinto the second vertebral body 12 b in the extended position.

In accordance with the illustrated embodiment, the first pair of pins 72extends superiorly and longitudinally distally from the crossbar 70 inthe superior channels 64, and the second pair of pins 74 extendsinferiorly and longitudinally distally from the crossbar 71 in theinferior channels 65. It should be appreciated, however, that the firstand second pairs of pins 72 and 74 can extend from the same crossbar ifdesired. The channels 64 and 65 can curve along their length along aconstant radius such that the pins 72 and 74 can be made from anysuitable rigid material, or the channels 64 and 65 can define differentcurvatures along their length, such that the pins 72 and 74 can be madeof any suitable flexible material. For instance the pins 72 and 74 canbe made from titanium or nitinol (nickel titanium). As will be describedin more detail below, the pins 72 and 74 are movable within the channels64 and 65 from the retracted position to the extended position wherebythe distal ends of the pins 72 and 74 extend out from the fixationhousing 36 and into the corresponding vertebral bodies 12 a and 12 bwhen the implant 10 is disposed in the intervertebral space 14. Thedistal ends of the pins 72 and 74 can extend out from the fixationhousing 36 substantially in the transverse direction T.

With continuing reference to FIGS. 2A-F, the actuator 40 is configuredto iterate the fixation member 38 from the retracted position to theextended position. In accordance with the illustrated embodiment, theactuator 40 can be provided as a screw 76 that defines external threads78 along part or all of the length of a screw shaft 89 that engagescorresponding internal threads 80 of the aperture 63. Accordingly, thescrew 76 can translate distally in the aperture 63 and thus the fixationhousing 36 as the screw 76 is rotated in the aperture 63 relative to thefixation housing 36. During operation, the screw 76 can translate alonga direction that has a longitudinal directional component (e.g.,distally) from a disengaged position to an engaged position. When thescrew 76 is in the disengaged position, the fixation member 38 is in theretracted position. When the screw 76 moves to the engaged position, thescrew 76 moves the fixation member 38 to the extended position.

Referring also to FIGS. 2G-J, the screw 76 defines a first engagementmember illustrated as a groove 82 that can extend circumferentially orabout an arc about the screw 76. The crossbars 70 and 71 definerespective apertures, which can be cylindrical, that extendslongitudinally through the crossbars 70 and 71, such that the crossbars70 and 71 define a respective collars 84 and 85 that are sized to beinserted into the groove 82. The collars 84 and 85 can becircumferentially sized slightly greater than the groove 82 such thatthe screw 76 is rotatable with respect to the collars. The longitudinaldimension of the collars 84 and 85 can be substantially equal to that ofthe groove 82 such that the collars 84 and 85, and thus the staples 68and 69, are substantially longitudinally fixed to the screw 76 such thatthe staples 68 and 69 translate as the screw 76 translates in theaperture 63. Thus, the pins 72 and 74 translate distally in therespective channels 64 and 65 to the extended position as the screw 76translates, whereby the distal ends of the pins 72 and 74, and thus thetips 73, extend transversely out from the fixation housing 36 to alocation transversely out from at least a portion of the implant body20. The distal ends of the channels 64 and 65 can extend substantiallytransversely such that the portion of the pins 72 and 74 that extend outfrom the channels 64 and 65, including the tips 73, can be directedsubstantially in the transverse direction into the respective vertebralbodies 12 a and 12 b.

The screw 76 defines an engagement member illustrated as a socket 86that extends longitudinally into the proximal end of the screw 76. Thesocket 86 is illustrated as a hexagonal in shape, though it could beshaped as any suitable polygonal shape, including a “plus” shape, a“dash” shape, or any alternative shape as desired. Because the socket 86extends longitudinally into the screw 76, the socket 86 defines a depththat is substantially parallel to the insertion direction of the implant10 into the intervertebral space 14. Accordingly, an anterior approachinto the intervertebral space 14 can facilitate both insertion of theimplant 10 into the intervertebral space and movement of the actuator 40from the disengaged position to the engaged position, therebycorrespondingly causing the fixation member 38 to move from theretracted position to the extended position.

Thus, an actuator tool, such as a hex drive, can be inserted into thesocket 86 and rotated, either manually or automatically so as to causethe screw 76 to rotate and translate distally relative to the fixationhousing 36. In accordance with the illustrated embodiment, the proximalend of the screw 76 extends longitudinally out to a location proximal ofthe front end 42 of the fixation housing 36 when the screw is in thedisengaged position. As the screw 76 translates distally to the engagedposition, the screw 76 translates distally until the screw 76 reachesthe engaged position. For instance, the aperture 63 can terminate at alocation that prevents further translation of the screw 76 once thescrew 76 has reached the engaged position. In accordance with theillustrated embodiment, proximal end of the screw 76 is substantiallyflush with the front end 42 of the fixation housing when the screw 76 isin the engaged position. As the screw 76 translates distally, thefixation member 38 likewise translates distally, which causes the pins72 and 74 to travel distally in their respective channels 64 and 65,thereby causing the tips 73 to initially protrude transversely from theupper and lower ends 46 and 48, respectively, of the fixation housing36. As the screw 76 and pins 72 and 74 continue to translate distally,the tips 73 extend increasingly out from the fixation housing 36 untilthe screw 76 is in the engaged position, at which point the tips 73 ofthe pins 72 and 74 are fully extended out from the fixation housing 36and into the vertebral bodies 12 a and 12 b.

If it is desired to retract the pins 72 and 74 so as to facilitateremoval of the implant 10 from the intervertebral space 14, the screw 76can be rotated relative to the fixation housing 36 in a second oppositedirection, thereby causing the screw 76 to translate proximally from theengaged position to the disengaged position. As the screw 76 translatesproximally, the fixation member 38 likewise translates proximally,thereby causing the tips of the pins 72 and 74 to retract toward therespective channels 64 and 65. When the screw 76 has been fullyretracted such that the screw is in the disengaged position, the tips 73of the pins 72 and 74 can be recessed with respect to the vertebralbodies 12 a and 12 b, and fully retracted in the respective channels 64and 65, at which point the implant 10 can be removed from theintervertebral space 14.

While the implant has been described in accordance with one embodiment,it should be appreciated that the implant 10 can be constructed inaccordance with any alternative embodiment as desired having at leastone fixation member that is configured to move between a retractedposition to an extended position as described above. A number of suchalternative embodiments are described below, it being appreciated thatthe embodiments are described herein for the purposes of illustration,and that other alternative embodiments are contemplated beyond thoseexplicitly described herein, for instance as defined by the appendedclaims.

For instance, referring to FIGS. 3A-C, the fixation assembly 22 of theimplant 10 is illustrated in accordance with an alternative embodiment,whereby the fixation housing 36 includes a pair of laterally spacedfixation housing segments 36 a and 36 b that are connected to thelateral sides 32 and 34 of the implant body 20. Each housing segment 36a and 36 b defines an aperture 63 that receives an actuator 40illustrated as a screw 76 in the manner described above. The superiorchannel 64 extends centrally from one of the apertures 63 in the housingsegment 36 b, and the inferior channel 65 extends centrally from theother aperture 63 in the housing segment 36 a. Each of the screws 76 candefine a bore 81 that extends centrally into their distal ends, suchthat the proximal ends of at least a first fixation member illustratedas a first pin 72 extends into the central bore 81 of the screw 76disposed in the housing segment 36 a. The first pin 72 further extendsinto the superior channel 64. The proximal ends of at least a secondfixation member illustrated as a pin 74 extends into the central bore 81of the screw 76 disposed in the housing segment 36 b, such that thesecond pin further extends into the inferior channel 64.

Referring also to FIGS. 3D-F, the proximal ends of the pins 72 and 74are rotatably coupled to the respective screws inside the bore 81, andcan be attached to the screws 76 via adhesive or weldments, or canalternatively be integrally connected to the screws 76. Thus, the pins72 and 74 are coupled to the respective screws 76 with respect to bothtranslation and rotation, such that the pins 72 and 74 both rotate andtranslate along with the respective screws 76 to which they areconnected. The pins 72 and 74 extend into the respective channels 64 and65, which extend superiorly and inferiorly, respectively, andlongitudinally distally as described above. Accordingly, the screws 76translate as they rotate in the housing 36 in the manner describedabove, which causes the pins 72 and 74 to rotate as they travel distallyin the respective channels 64 and 65. The tips 73 therefore also rotateas they translate out from the fixation housing 36. The pins 72 and 74can each include a cutting bit, for instance cutting flutes 83, at theirtips 73 so as to facilitate cutting into the vertebral bodies 12 a and12 b as the pins 72 rotate and translate from their retracted positionsto their extended positions.

The screws 76, channels 64 and 65, and pins 72 and 74, can extendsubstantially parallel to each other (longitudinally as illustrated inFIGS. 3A-F), or can be angularly offset with respect to each other. Forinstance, the screws 76 and the channels 64 and 65, and thus the pins 72and 74, can converge toward each other along a direction from theirproximal ends to their distal ends as illustrated in FIG. 3G.Alternatively still, the channels 64 and 65 can diverge away from eachother along a direction from their proximal ends to their distal ends.

Alternatively still, the implant 10 can include a pair of screws 76 ateach lateral side 32 and 34. For instance, each side 32 and 34 caninclude a superior screw 76 coupled to a superior pin in the mannerdescribed above, and an inferior screw 76 located inferior with respectto the superior screw and coupled to an inferior pin in the mannerdescribed above, such that each lateral side of the implant body 20 canbe fixed to both the superior vertebral body 12 a and the inferiorvertebral body 12 b.

Referring now to FIGS. 4A-C, the fixation assembly 22 of the implant 10is illustrated in accordance with an alternative embodiment, whereby thelaterally spaced fixation housing segments 36 a and 36 b each include asuperior aperture 63 a and an inferior aperture 63 b that each receivean actuator 40 illustrated as a superior screw 76 a and an inferiorscrew 76 b in the manner described above. The superior aperture 63 a andthe inferior aperture 63 b can be laterally displaced from each other bya distance at least equal to the thickness of the channels 64 and 65.Accordingly, the superior channel 64 can extend from the inferioraperture 63 b and the inferior channel 65 can extend from the superioraperture 63 a, such that the channels 64 and 65 in each housing segment36 a and 36 b cross over each other and can be longitudinally andtransversely aligned without interfering with each other.

The superior channels 64 extend centrally from the inferior apertures 63in the housing segments 36 a and 36 b, and the inferior channels 65extend centrally from the apertures 63 in the housing segments 36 a and36 b. Each of the screws 76 a and 76 b can define a bore 81 that extendscentrally into their distal ends. The proximal ends of at least a firstfixation member 38 such as a pair of first fixation members illustratedas a pair of first pins 72 extends into the central bore 81 of thecorresponding pair of the inferior screws 76 b that are disposed in theinferior apertures 63 b and aligned with the superior channels 64. Thefirst pins 72 further extend into the superior channels 64 from theinferior screws 76 b. The proximal ends of at least a second fixationmember such as a pair of second fixation members illustrated as a pairof second pins 74 extends into the central bore 81 of the correspondingpair of superior screws 76 a that are disposed in the superior apertures63 a and aligned with the inferior channels 65. The second pins 74further extend into the inferior channels 65 from the superior screws 76a.

Referring also to FIGS. 4D-F, the proximal ends of the pins 72 and 74are rotatably coupled to the respective screws 76 a and 76 b inside thebore 81, and can be attached to the screws 76 a and 76 b via adhesive orweldments, or can alternatively be integrally connected to the screws 76a and 76 b. Thus, the pins 72 and 74 are coupled to the respectivescrews 76 b and 76 a with respect to both translation and rotation, suchthat the pins 72 and 74 rotate and translate with the respective screws76 b and 76 a to which they are connected. The pins 72 extend into thesuperior channels 64 from the inferior screws 76 b, and the pins 74extend into the inferior channels 65 from the superior screws 76 a.

Both channels 64 and 65 extend from the respective apertures 63 b and 63a in a direction having both longitudinal and transverse directionalcomponents. The proximal ends of the superior channels 64 are inferiorwith respect to the proximal ends of the inferior channels 65, and thedistal ends of the superior channels 64 are superior with respect to thesuperior ends of the inferior channels 65. For instance, the distal endsof the superior channels 64 extend through the top end of the fixationhousing 36 and/or implant body 20. The distal ends of the inferiorchannels 64 extend through the bottom end of the fixation housing 36and/or implant body 20. During operation, the screws 76 translate asthey rotate in the housing 36 in the manner described above, whichcauses the pins 72 and 74 to rotate as they travel distally in therespective channels 64 and 65. The tips 73 therefore also rotate as theytranslate out from the fixation housing 36. The pins 72 and 74 can eachinclude a cutting bit, for instance cutting flutes 83, at their tips 73so as to facilitate cutting into the vertebral bodies 12 a and 12 b asthe pins 72 rotate and translate from their retracted positions to theirextended positions. The pins 72 that are connected to the inferiorscrews 76 b extend through the superior channels 64 such that the tips73 extend transversely outward with respect to the fixation housing 36and for the implant body 20 along a direction having a transversedirectional component into the superior vertebral body 12 a when theimplant 10 is disposed in the intervertebral space 14 and the pins 72have been iterated to their extended position. The pins 74 that areconnected to the superior screws 76 a extend through the inferiorchannels 65 such that the tips 73 extend transversely outward withrespect to the fixation housing 36 and/or the implant body 20 along adirection having a transverse directional component into the inferiorvertebral body 12 b when the implant 10 is disposed in theintervertebral space 14 and the pins 74 have been iterated to theirextended position.

The channels 64 and 65 can extend substantially parallel to each other(longitudinally as illustrated in FIGS. 4A-F), or can be angularlyoffset with respect to each other. For instance, the channels 64 and 65can converge toward each other along a direction from their proximalends to their distal ends as illustrated in FIG. 4G. Alternativelystill, the channels 64 and 65 can diverge away from each other along adirection from their proximal ends to their distal ends.

Referring now to FIGS. 5A-G, the fixation assembly 22 of the implant 10is illustrated substantially as described with respect to FIGS. 4A-G,however the pins 72 and 74 can include external threads 87 along part orall of their length, for instance at the terminal end that extendstransversely out from the fixation housing 36. Accordingly, as the pins72 and 74 rotate to their extended position, the threads 87 engage thevertebral bodies 12 a and 12 b. The threads 87 can have a pitch that isthe same or different than the pitch of the external threads 78 of thecorresponding screws 76. Furthermore, the pins 72 and 74 are illustratedas integral with the screws 76 a and 76 b.

Referring now to FIGS. 6A-6D, the actuation assembly 22 includes a pairof fixation members 38 in the form of a first superior staple 68 and asecond inferior staple 69. The first staple 68 includes a base in theform of a crossbar 70 and at least a first pair of laterally spaced pins72 that extend out from the crossbar 70 at any location, such as atopposed outer ends of the crossbar 70 as illustrated. The second staple69 can further include a second pair of laterally spaced pins 74 thatextend out from base illustrated as a second crossbar 71 at anylocation, such as at opposed outer ends of the crossbar 71 asillustrated. The staples 68 and 69 can be disposed in respectivesuperior and inferior channels 64 and 65 that can extend in anydirection desired, such as the transverse direction as illustrated. Itshould be appreciated that the channels 64 and 65 can be continuous in asingle channel, or bifurcated and separate as desired.

The actuator 40 can be provided as a screw 76 that is configured toiterate the fixation members 38 from the retracted position in which thetips 73 are recessed with respect to the fixation housing 36 and/or theimplant body 20 to the extended position in which the tip 73 extendtransversely out from the fixation housing 36 and/or the implant body20. In accordance with the illustrated embodiment, the actuator 40 canbe provided as a screw 76 that defines external threads 78 along part orall of its length that engages corresponding internal threads 80 of theaperture 63. Accordingly, the screw 76 can translate distally in theaperture 63 and thus the fixation housing 36 as the screw 76 is rotatedin the aperture 63 relative to the fixation housing 36.

The screw 76 defines a beveled distal tip 88 that tapers transverselyinwardly along a longitudinal distal direction. During operation, thescrew 76 can translate from a disengaged position to an engagedposition. When the screw 76 is in the disengaged position, the fixationmember 38 is in the retracted position. When the screw 76 moves to theengaged position, the screw 76 moves the fixation member 38 to theextended position.

When the staples 68 and 69 are in their retracted positions, therespective crossbars 70 and 71 are disposed adjacent each other, andthus separated by a first distance that can be equal to substantiallyzero such that the staples 68 and 69 abut each other. The crossbars 70and 71 can be round in cross-section or otherwise shaped so as to definerespective first and second cam surfaces 90 and 92 that can extendtransversely inward along a longitudinal distal direction so as tocreate a gap between a proximal portion of the crossbars 70 and 71 ifthey abut each other when in their retracted positions.

Referring also to FIGS. 6E-F, during operation, the screw 76 translatealong the longitudinally distal direction, such that the screw 76 canengage, or ride along, the first and second cam surfaces 90 and 92 ofthe staples 68 and 69, thereby causing the pins 72 and 74 to translatealong the channel in a direction having a transverse directionalcomponent. For instance, the channels 64 and 65 can guide the pins totranslate pins 72 and 74 substantially in the transverse direction withrespect to the fixation housing 36. In particular, as the screw 76translates distally in the housing, the beveled tip 88 engages the camsurfaces 90 and 92 of the staples 68 and 69. Because the beveled tip 88is tapered, the tip 88 biases the staples 68 and 69 transversely outwardas the screw 76 continues to translate distally. Thus, the beveled tip88 can be said to define a third cam surface configured to engage thefirst and second cam surfaces 90 and 92 substantially simultaneously soas to cause terminal ends 73 of the pins 72 and 74 to translate in thetransverse direction until the screw 76 reaches the engaged position.When the screw 76 is in the engaged position, staples 68 and 69 can bein their extended positions such that the pins 72 extend superiorly outthe fixation housing 36 and the pins 74 extend inferiorly out thefixation housing 36. Accordingly, the pins 72 extend into the superiorvertebral body 12 a and the pins 74 extend into the inferior vertebralbody 12 b when the implant 10 is disposed in the intervertebral space14. The staples 68 and 69, including the crossbars 70 and 71 and thepins 72 and 74 can be substantially rigid or flexible as desired.

It should be appreciated that the tip 88 of the screw 76 can beconfigured to bias the staples 68 and 69 transversely outward as thescrew 76 moves in the longitudinally distal direction if either the camsurfaces 90 and 92 are angularly offset with respect to the transversedirection, or if tip 88 of the screw is angularly offset with respect tothe transverse direction. In accordance with the illustrated embodiment,all cam surfaces 90 and 92 along with the cam surface defined by thebeveled tip 88 are angularly offset with respect to the transversedirection. The cam surfaces can be substantially planar, curved, bent,or otherwise shaped as desired.

Referring now also to FIGS. 6G-H, the fixation assembly 22 can furtherinclude a second actuator in the form of an extractor 96 that isconfigured to engage the crossbars of the first and second staples 68and 69 so as to cause terminal ends 73 of the pins 72 of the firststaple 68 to retract inferiorly into the fixation housing 36 and furtherto cause the terminal ends 73 of the pins 74 of the second staple 69 toretract superiorly into the housing.

The extractor 96 can be provided as a screw 98 that defines anexternally threaded shaft 100 along part or all of its length thatengages the internal threads 80 of the aperture 63 in the fixationhousing 36. Accordingly, the screw 98 can translate distally in theaperture 63 and thus the fixation housing 36 as the screw 98 is rotatedin the aperture 63 relative to the fixation housing 36. The screw 98further defines a collar 102 at its distal end that is rotatable withrespect to the threaded shaft 10. The collar 102 defines at least onebeveled surface such as a pair of beveled surfaces 104 and 106 that canbe angularly offset with respect to the transverse direction. Inaccordance with the illustrated embodiment, the beveled surfaces 104 and106 are tapered toward each other along a proximal direction oppositethe distal direction of insertion of the screw 98.

The crossbars 70 and 71 can define respective first and secondextraction cam surfaces 108 and 110 that are configured to engage thebeveled surfaces 104 and 106, respectively, of the extractor 96. Theextraction cam surfaces 108 and 110 can be provided by notches 112 and114 that extend transversely inward into, but not through, thetransverse outer surfaces of the crossbars 70 and 71. The notches 112and 114 can be sized so as to receive the respective beveled surfaces104 and 106. The extraction cam surfaces 108 and 110 can be angularlyoffset with respect to the transverse direction, or can extend in anydirection as desired. The extraction cam surfaces 108 and 110, and thebeveled surfaces 104 and 106 can extend substantially planar, can becurved, bent, or otherwise shaped as desired.

During operation, the screw 76 can be removed after the staples 68 and69 have been iterated to their extended positions, or otherwise out fromtheir retracted positions. The screw 98 can translate distally in thefixation housing 36 from a disengaged position to an engaged position.When the screw 98 is in the disengaged position, the staples 68 and 69remain in their extended position as actuated by the screw 76. When thescrew 98 moves to the engaged position, the screw 98 iterates thestaples 68 and 69 to their retracted positions. In particular, as thescrew 98 translates from the disengaged position to the engagedposition, the beveled surfaces 104 and 106 contact the crossbars 70 and71, for instance in the notches 112 and 114, which can remain in thefixation housing 36 when the staples 68 and 69 are in their fullyextended positions.

Because the collar 102 is rotatable with respect to the threaded screwshaft 100, the beveled surfaces 104 and 106 remain engaged in thenotches 112 and 114 as the screw shaft 100 continues to rotate withrespect to the fixation housing 36 to translate the screw 98 distally inthe fixation housing 36. The fixation housing 36 can define a channelthat receives the collar so as to maintain the beveled surfaces 104 and106 in alignment with the notches 112 and 114 as the screw 98 rotates inthe fixation housing 36. As the screw 98 translates distally, thecrossbars 70 and 71 ride along the beveled surfaces 104 and 106. Thebeveled surfaces 104 therefore bias the staples 68 and 69 so as to movetransversely inward toward the central longitudinal axis 37. Thus, thesuperior staple 68 and corresponding pins 72 translate inferiorly untilthe pins 72 are removed from the superior vertebral body 12 a andrecessed in the fixation housing 36. The implant 10 can then be removedfrom the intervertebral space 12 or repositioned in the intervertebralspace 12 as desired. Furthermore, the inferior staple 69 andcorresponding pins 74 translate superiorly until the pins 74 are removedfrom the inferior vertebral body 12 b and recessed in the fixationhousing. Thus, the beveled surfaces 104 and 106 can be referred to ascam surfaces that cause the fixation members 38 to move in a directionfrom their extended positions toward their retracted positions.

In accordance with the illustrated embodiment, the extractor 96 can beprovided as a discrete actuator with respect to the actuator 40. Inaccordance with an alternative embodiment, the extractor 96 can beattachable to the actuator 40 or integrally formed with the actuator 40,such that one longitudinal side of the actuator 40 defines the distaltip 88 and the opposed longitudinal side of the actuator 40 includes thecollar 102.

Referring now to FIGS. 7A-C, the fixation assembly 22 can be constructedin accordance with an alternative embodiment. The fixation assembly 22can include at least one actuator 40 that is configured to iterate atleast one fixation member 38 between a retracted position and anextended position in the manner described above. The fixation assembly22 can further include a biasing member 118 that is operably coupledbetween the actuator 40 and the fixation member 38. For instance, thebiasing member 118 can be attached to the fixation member 38 at itsdistal end, and can move the fixation member 38 from the retractedposition to the extended position under forces applied to the biasingmember 118 by the actuator 40.

The at least one fixation member 38 can be in the form of a firstsuperior fixation member illustrated as a first superior staple 68, anda second inferior fixation member illustrated as a second inferiorstaple 69 as described above. Thus, the first staple 68 includes a basein the form of a crossbar 70 and at least a first pair of laterallyspaced pins 72 that extend out from the crossbar 70 at any location,such as at opposed outer ends of the crossbar 70 as illustrated. Thesecond staple 69 can further include a second pair of laterally spacedpins 74 that extend out from a base in the form of a second crossbar 71at any location, such as at opposed outer ends of the crossbar 71 asillustrated. The staples 68 and 69 can be disposed in respectivesuperior and inferior channels 64 and 65 that can extend in anydirection desired, such as the transverse direction as illustrated. Itshould be appreciated that the channels 64 and 65 can be continuous in asingle channel, or bifurcated and separate as desired.

In accordance with the illustrated embodiment, the actuator 40 can beprovided as a screw 76 that defines external threads 78 along part orall of the longitudinal length of the screw shaft 89. The screw 76defines a screw head 91 that defines an outer cam surface 93 and iscoupled to the distal end of the screw shaft 89, and can have across-sectional dimension (e.g., diameter) greater than that of thescrew shaft 89. The threads 78 engage corresponding internal threads 80of the aperture 63 in the front end 42 of the fixation housing 36.Accordingly, the screw 76 can translate distally in the aperture 63 andthus the fixation housing 36 as the screw 76 is rotated in the aperture63 relative to the fixation housing 36. During operation, the screw 76can translate from a disengaged position to an engaged position. Whenthe screw 76 is in the disengaged position, the fixation member 38 is inthe retracted position. When the screw 76 moves to the engaged position,the screw 76 moves the fixation member 38 to the extended position.

The biasing member 118 includes a first superior flexible biasing arm120 and a second inferior flexible biasing arm 122. The arms 120 and 122define respective proximal ends 124 and 126 that extend transverselyinward with respect to a pair of intermediate segments 132 and 134 thatare tapered transversely toward each other along the distal longitudinaldirection. The proximal ends 124 and 126 are fixed to the fixationhousing 36 at respective connection locations 123 and 125 via anadhesive, mechanical fastener, or friction fit, or any suitablealternative fixation. The arms 120 and 122 define distal ends in theform of hooks 133 that are fastened to the crossbars 70 and 71. Theintermediate segments 132 and 134 are connected between the proximal anddistal ends of the flexible arms 120 and 122. The intermediate segments132 and 134 are connected to the proximal ends 124 and 126 by a hinge127. The hooks 133 are transversely spaced from each other by adistance, which can equal zero if they abut, that is less than thetransverse dimension of the screw cam surface 93 when the staples 68 and69 are in their retracted positions.

Referring also to FIGS. 7D-F, as the screw 76 translates distally fromits disengaged position to its engaged position, the outer cam surface93 of the screw 76 is configured to contact and ride along the flexiblearms 120 and 122 substantially simultaneously. The flexible arms 120 and122 can thus define inner cam surfaces that engage the outer cam surface93 of the screw 76. The outer cam surface 93 defines a transversedimension such that as the cam surface 93 rides along the intermediatesegments 132 and 134, the flexible arms 120 and 122 flex transverselyoutward about the hinge 127, thereby causing the hooks and correspondingpins 72 and 74 to translate transversely outward in their respectivechannels 64 and 65 to their extended positions as illustrated in FIG.7F, whereby the terminal tips 73 of the pins 72 extends superiorly outthe fixation housing 36, and the terminal tips 73 of the pins 74 extendinferiorly out the fixation housing 36. In this regard, the innertransverse surfaces of the intermediate segments 132 and 134 can bereferred to as cam surfaces.

Referring now to FIG. 8A-B, the biasing arms 120 and 122 canalternatively be substantially rigid so as to not flex in response toengagement by the actuator 40. In particular, the biasing arms 120 and122 are pivotally connected to the fixation housing 36, for instance atthe hinges 127. Thus, the biasing arms 120 and 122 can pivot relative tothe fixation housing 36 about a lateral pivot axis. The proximal ends124 and 126 can be detached from the flex housing 36, and are disposedin the aperture 63 in accordance with the illustrated embodiment. Thedistal ends can be provided as hooks that are connected to fixationmembers as described above with respect to FIGS. 7A-F, or canalternatively include integral fixation pins 72 and 74, respectively.

The actuator 40 can be provided as a screw 76 that defines externalthreads 78 along part or all of the length of a screw shaft 89 thatengages corresponding internal threads 80 of the aperture 63.Accordingly, the screw 76 can translate distally in the aperture 63 andthus the fixation housing 36 as the screw 76 is rotated in the aperture63 relative to the fixation housing 36. During operation, the screw 76can translate distally from a disengaged position to an engagedposition. The distal end of the screw 76 can define a cam surface 93that is sized to contact the proximal ends 124 and 126 of the biasingarms 120 and 122. Thus, the longitudinal proximal surfaces of theproximal ends 124 and 126 present respective cam surfaces that areconfigured to receive a longitudinal biasing force that causes thebiasing arms 120 and 122 to pivot, which in turn causes the superior andinferior fixation pins 72 and 74, respectively, to extend superior andinferior of the housing 36 into the respective superior and inferiorvertebral bodies 12 a and 12 b.

Referring now to FIGS. 9A-B, the fixation assembly 22 can be constructedgenerally as a propeller in accordance with an alternative embodiment.The fixation housing 36 can be positioned such that the rear end 44 isaligned with the central opening 25 of the implant body 20 and the frontend 42 is displaced proximal of the front end 24 of the implant body 20.The fixation assembly 22 includes an actuator 40 in the form of arotatable hub or shaft 89 that is connected to the fixation housing 36so as to be rotatable with respect to the fixation housing 36 andtranslatably fixed to the housing. The rotatable shaft 89 can bethreaded or unthreaded, and can be configured so as to maintain asubstantially fixed longitudinal position (and thus does notsubstantially translate proximally or distally) as it rotates relativeto the fixation housing 36. The shaft 89 defines an engagement memberillustrated as a socket 86 that extends longitudinally into the proximalend of the shaft 89. The socket 86 is illustrated as a hexagonal inshape, though it could be shaped as any suitable polygonal shape,including a “plus” shape, a “dash” shape, or any alternative shape asdesired so as to receive a drive member that actuates the shaft torotate.

The at least one fixation member 38 can include at least one pair offixation blades such as first superior fixation blade 142 and a secondinferior fixation blade 144 that are rotatably coupled to the shaft 89such that the blades 142 and 144 rotate along with the shaft 89. Inaccordance with the illustrated embodiment, the fixation member 38includes a first proximal pair of a superior blade 142 and an inferiorblade 144, and a second distal pair of a superior blade 142 and aninferior blade 144. The first pair of blades 142 and 144 is disposedproximal of the front end 24 of the implant body 20, and the second pairof blades 142 and 144 is disposed in alignment with the central cavity25 of the implant body 20. Both pairs of blades 142 and 144 can berotatably coupled to the shaft 89 so as to rotate along with the shaft89. The blades 142 and 144 can be substantially planar in the lateraland transverse directions A and T, or can be curved if desired (forinstance if the blades 142 and 144 are translatable with respect to theshaft 89, or of the shaft 89 is translatable with respect to thefixation housing 36. The blades 142 and 144 can taper to a distalterminal tip 143. Each blade 142 and 144 presents a leading edge 145 anda trailing edge 146 with respect to movement from the retracted positionto the extended position.

Referring also to FIG. 9C, the fixation housing 36 defines a channelillustrated as a slot that allows the blades 142 and 144 to rotate fromtheir retracted positions to their extended positions. In particular,the fixation housing 36 defines a superior blade slot 148 that receivesthe superior blade 142 and an inferior blade slot 150 that receives theinferior blade 144. The inferior and superior blade slots 148 and 150are both laterally and transversely opposed, and dimensioned such thatthe blades 142 and 144 can rotate from a first retracted positionwhereby the tips 143 are transversely recessed with respect to thevertebral bodies 12 a and 12 b, respectively, for instance in thefixation housing 36 to a second extended position whereby the tips 143extend transversely out from the fixation housing 36 ad into therespective vertebral bodies 12 a and 12 b when the implant 10 isdisposed in the intervertebral space 14. For instance, the slots 148extend through both the top and lateral ends 46 and 50 of the fixationhousing body 36. The slots 150 extend through both the bottom andlateral ends 48 and 52 of the fixation housing 36. The first pair ofslots 148 and 150 is disposed proximal of the front end of the fixationhousing 36, and the second pair of slots 148 and 150 is aligned with thecentral cavity 25.

During operation, the shaft 89 rotates from a first rotationaldisengaged position whereby the fixation blades 142 and 144 are in therecessed position to an second rotational engaged position whereby thefixation blades 142 and 144 are in the extended position. The shaft 89can rotate along an angle between 0 degrees and 180 degrees, such asbetween 20 degrees and 90 degrees, between the disengaged and theengaged position. The blades 142 and 144 can extend radially out fromthe shaft 89 through the respective blade slots 148 and 150 such thatthe tips 143 are disposed laterally out from the fixation housing in theintervertebral space 14 when the blades 142 and 144 are in theirretracted positions. The fixation housing 36 provides stops at thelateral ends of the slots 148 and 150 in the top and bottom ends 46 and50 that prevent the blades 142 and 144 from over-rotating past theextended positions.

As illustrated in FIGS. 9A-C, the leading and trailing edges 145 and 146can extend substantially straight in a radially outward direction fromthe shaft 89 to the tips 143. Alternatively, one or both of the leadingand trailing edges 145 and 146 can be curved as desired in a radiallyoutward direction from the shaft 89 toward the tips 143. For instance,as illustrated in FIGS. 9D-E, the leading edges 145 can be concave andthe trailing edges 146 can be convex. Alternatively, either or both ofthe leading and trailing edges 145 and 146 can be straight, concave,convex, or otherwise curved as desired.

Referring now to FIGS. 10A-C, the fixation assembly 22 is constructedsubstantially as described with respect to the fixation assembly asillustrated in FIGS. 9A-C. However, the fixation blades 142 and 144 asillustrated in FIGS. 10A-C can be constructed extend radially out fromthe shaft 89 a distance less than that of the blades 142 and 144 asillustrated in FIGS. 9A-C. Therefore, when the blades 142 and 144 are intheir retracted positions, the blades 142 and 144 are disposed in thefixation housing 36. The superior blade slots 148 can extend through thetop end 46 of the fixation housing 36 and not through either lateral endof the fixation housing. Likewise, the inferior blade slots 150 canextend through the top end 46 of the fixation housing 36 and not througheither lateral end of the fixation housing.

Referring now to FIGS. 11A-B, the fixation assembly 22 can include therotatable shaft 89 supported in the fixation housing 36 substantially asdescribed above with respect to FIGS. 9A-C. Thus, the fixation assembly22 includes an actuator 40 in the form of a rotatable shaft 89 that isconnected to the fixation housing 36 so as to be rotatable with respectto the fixation housing 36 and translatably fixed to the housing. Therotatable shaft 89 can be threaded or unthreaded, and can be configuredso as to maintain a substantially fixed longitudinal position (and thusdoes not substantially translate proximally or distally) as it rotatesrelative to the fixation housing 36. The shaft 89 defines an engagementmember illustrated as a socket 86 that extends longitudinally into theproximal end of the shaft 89. The socket 86 is illustrated as ahexagonal in shape, though it could be shaped as any suitable polygonalshape, including a “plus” shape, a “dash” shape, or any alternativeshape as desired so as to receive a drive member that actuates the shaftto rotate.

The shaft 89 defines an outer circumferential surface 141 and at leastone groove 147 that extends radially into the circumferential surface141 and receives at least one fixation member 38, such as a pair offixation members 38. The shaft 89 can alternatively define a pair oflongitudinally spaced grooves. The groove 147 can extend around aportion of or the entirety of the circumference of the shaft 89, or canalternatively include a pair of discrete grooves that each receives apair of fixation members 38.

The at least one fixation member 38 can include a first superior staple68 and a second inferior staple 69 coupled to the shaft 89 in the firstproximal groove 147, and a first superior staple 68 and a secondinferior staple 69 coupled to the shaft 89 in the second distal groove147. The staples 68 and 69 can extend out from the shaft 89 inrespective superior and inferior channels 64 and 65 that extend into orthrough the fixation housing 36. The first staple 68 includes a base inthe form of a crossbar 70 and at least a first pair of laterally spacedpins 72 that extend out from the crossbar 70 at any location, such as atopposed outer ends of the crossbar 70 as illustrated. The second staple69 can further include a second pair of laterally spaced pins 74 thatextend out from base illustrated as a second crossbar 71 at anylocation, such as at opposed outer ends of the crossbar 71 asillustrated. The staples 68 and 69 can be disposed in respectivesuperior and inferior channels 64 and 65 that can extend in anydirection desired, such as the transverse direction as illustrated. Itshould be appreciated that the channels 64 and 65 can be continuous in asingle channel, or bifurcated and separate as desired. The staples 68and 69 can define terminal tips 73 that can be rigid, and extendtangentially out from the shaft 89 and into the respective channels 64and 65. At least a portion of the proximal portion of the staples 68 and69 can be flexible so as to wrap around the shaft 89 when the staples 68and 69 are in the retracted position, and extend tangentially out fromthe shaft 89 when the staples 68 and 69 are in the extended position.

Referring also to FIG. 11C, during operation, the shaft 89 rotates froma first rotational disengaged position whereby the staples 68 and 69 arein the recessed position to an second rotational engaged positionwhereby the staples 68 and 69 are in the extended position. The staples68 and 69 can travel in their respective channels 64 as they move fromtheir retracted positions to their extended positions. When the staples68 and 69 are in the retracted positions, the tips 63 are disposed inthe housing 36 and do not extend into the respective vertebral bodies 12a and 12 b. When the staples 68 and 69 are moved to the extendedpositions, the tips 63 extend transversely out from the fixation housing36 and into the vertebral bodies 12 a and 12 b. The fixation housing 36can provide any suitable stop that prevents the shaft 89 fromover-rotating past the engaged position.

Referring now to FIGS. 11D-F, the tips 73 of the staples 68 and 69 canbe flexible, and can be disposed substantially entirely in the groove147 of the shaft 89 when the shaft 89 is in the disengaged position andthe staples 68 and 69 are in the corresponding retracted position. Thus,when the shaft 89 rotates from the disengaged position to the engagedposition, the tips 73 extend into the respective channels 64 and 65until the shaft 89 is in the engaged position which causes the staples68 and 69 to move to the extended position such that the tips 73 extendout from the fixation housing 36 and into the adjacent vertebral bodies12 a and 12 b.

Referring to FIGS. 12A-C, the fixation assembly 22 can be constructedsubstantially as described above with respect to FIGS. 11A-C, howeverthe shaft 89 can include gear teeth 152 that are longitudinally elongateand circumferentially spaced about the outer circumference 141 of theshaft 89. The staples 68 can include a complementary rack 154 of teeth156 that are configured to mate with the gear teeth 152 of the shaft 89as the shaft rotates so as to drive the tips 73 into the vertebralbodies 12 a and 12 b in the manner described above. The rack 154 can beflexible, and the tips 73 can be flexible or rigid as desired. It shouldbe appreciated that the shaft 89 can be rotated in an opposite directionfrom the engaged position to the disengaged position so as to cause thestaples 68 and 69 to retract from the extended position to the retractedposition.

Referring now to FIGS. 13A-C, the fixation assembly 22 of the implant 10is illustrated in accordance with an alternative embodiment, whereby thefixation housing 36 includes a pair of laterally spaced fixation housingsegments 36 a and 36 b that are connected to the lateral sides 32 and 34of the implant body 20. Each housing segment 36 a and 36 b defines anaperture 63 that receives an actuator 40 illustrated as a shaft 89 inthe manner described above. The shafts 89 can each be configured as aworm gear 155 having a corresponding helical gear tooth 157 that extendslongitudinally about the circumference 141 of the shaft 89.

The fixation assembly 22 can further include at least one fixationmember 38 illustrated as a first superior pin 72 having a tip 73 thatfaces transversely down, and a second inferior pin 74 having a tip 73that faces transversely up. The pins 72 and 74 can each include ahelical gear tooth 158 that is configured to mate with the gear teeth157 of the respective shafts 89. The pins 72 and 74 are disposed incorresponding first and second superior and inferior channels 64 and 65,respectively, that extend transversely in the fixation housing 36.During operation, the shaft 89 can be disposed in a first disengagedposition whereby the tips 73 are recessed in the fixation housing 36 andthus do not extend into the adjacent vertebral bodies 12 a and 12 b whenthe implant 10 is disposed in the intervertebral space 10. Referring toFIGS. 13D-E, the shaft 89 can be rotated to the engaged position, whichcauses the worm gear 155 to drive the gear tooth 158, thereby causingthe pins 72 and 74 to translate transversely superiorly and inferiorly,respectively, until the tips 73 are inserted into the respectivevertebral bodies 12 a and 12 b. The tips 73 can include cutting flutesand/or can be threaded as desired in the manner described above toenhance fixation in the vertebral bodies 12 a and 12 b.

As illustrated in FIG. 13A, the shafts 89 can extend substantiallyparallel to each other in the respective fixation housing segments 36 aand 36 b. Alternatively, as illustrated in FIG. 13F, the shafts 89 canbe angularly offset with respect to each other. For instance, thechannels shafts 89 can converge toward each other along a direction fromtheir proximal ends to their distal ends as illustrated in FIG. 3F.Alternatively still, the shafts 89 can diverge away from each otheralong a direction from their proximal ends to their distal ends.

Referring now to FIGS. 14A-B, the fixation assembly 22 can include therotatable shaft 89 supported in the fixation housing 36 substantially asdescribed above with respect to FIGS. 11A-C. Thus, the fixation assembly22 includes an actuator 40 in the form of a rotatable shaft 89 that isconnected to the fixation housing 36 so as to be rotatable with respectto the fixation housing 36 and translatably fixed to the fixationhousing 36. The rotatable shaft 89 can be threaded or unthreaded, andcan be configured so as to maintain a substantially fixed longitudinalposition (and thus does not substantially translate proximally ordistally) as it rotates relative to the fixation housing 36. The shaft89 defines an engagement member illustrated as a socket 86 that extendslongitudinally into the proximal end of the shaft 89. The socket 86 isillustrated as a hexagonal in shape, though it could be shaped as anysuitable polygonal shape, including a “plus” shape, a “dash” shape, orany alternative shape as desired so as to receive a drive member thatactuates the shaft to rotate.

The shaft 89 can define a proximal surface 160 and a distal surface 162,and at least one bore that extends longitudinally through the shaft 89between the proximal and distal surfaces 162. The shaft 89 can include afirst superior bore 164 a and a second inferior bore 164 b that extendsthrough the shaft at a location 180 degrees offset with respect to thefirst bore 164 a. The fixation assembly 22 can include at least fixationmember 38 in the form of a first superior staple 68 and a secondinferior staple 69. The first staple 68 includes a base in the form of acrossbar 70 and at least a first pair of laterally spaced pins 72 thatextend out from the crossbar 70 at any location, such as at opposedouter ends of the crossbar 70 as illustrated. The second staple 69 canfurther include a second pair of laterally spaced pins 74 that extendout from base illustrated as a second crossbar 71 at any location, suchas at opposed outer ends of the crossbar 71 as illustrated.

The crossbars 70 and 71 of the staples 68 and 69 can extendlongitudinally through the first and second bores 164 a and 164 b,respectively. The crossbars 70 and 71 can be loosely received in thefirst and second bores 164 a and 164 b such that the crossbars 70 and 71are rotatable inside the bores 164 a and 164 b. Thus, the staples 68 and69 and associated pins 72 and 74 can pivot relative to the shaft 89about a longitudinal pivot axis defined by the crossbars 70 and 71,respectively. It can thus be said that the pins 72 and 74 are connectedto the shaft 89 at a location inwardly spaced with respect to the outercircumference 141 of the shaft 89. The pins 72 and 74 extend out fromthe crossbars 70 and 71 and the shaft 89 along a substantiallytransverse direction in respective superior and inferior channels 64 and65. The pins 72 and 74 can be flexible or rigid as desired, and canextend along the adjacent proximal and distal shaft surfaces so as tofix the staples 68 and 69 with respect to translation relative to theshaft 89.

Referring also to FIG. 14C, during operation, the shaft 89 rotates froma first rotational disengaged position whereby the staples 68 and 69 arein the recessed position to an second rotational engaged positionwhereby the staples 68 and 69 are in the extended position. The staples68 and 69 can travel in their respective channels 64 as they move fromtheir retracted positions to their extended positions. As the shaft 89rotates about a longitudinal axis from the disengaged position to theengaged position, the pins 72 and 74 can pivot about a longitudinal axisso as to remain substantially transversely oriented as the tips 73project out from the fixation housing 36 and into the adjacent vertebralbodies 12 a and 12 b. When the staples 68 and 69 are in the retractedpositions, the tips 63 are disposed in the housing 36 and do not extendinto the respective vertebral bodies 12 a and 12 b. The fixation housing36 can provide any suitable stop that prevents the shaft 89 fromover-rotating past the engaged position. It should be appreciated thatthe shaft 89 can be rotated in an opposite direction from the engagedposition to the disengaged position so as to cause the staples 68 and 69to retract from the extended position to the retracted position.

It should be noted that, unless otherwise specified, the term “or” isused in its nonexclusive form (e.g. “A or B” includes A, B, A and B, orany combination thereof, but does not have to include all of thesepossibilities). It should be noted that, unless otherwise specified,“and/or” is used similarly (e.g. “A and/or B” includes A, B, A and B, orany combination thereof, but does not have to include all of thesepossibilities). It should be noted that, unless otherwise specified, theterm “includes” means “comprises” (e.g. a device that includes orcomprises A and B contains A and B but optionally may contain C oradditional components other than A and B). It should be noted that,unless otherwise specified, the singular forms “a,” “an,” and “the”refer to one or more than one, unless the context clearly dictatesotherwise.

Although the invention has been described with reference to preferredembodiments or preferred methods, it is understood that the words whichhave been used herein are words of description and illustration, ratherthan words of limitation. For instance, it should be appreciated thatwhile the intervertebral implant has been described herein as configuredto fix to adjacent vertebral bodies, the implant can alternatively beinserted into a space between any bones or bone segments (e.g.,fractured bone segments) as desired, and subsequently fixed to theadjacent bones or bone segments in the manner described herein.Furthermore, although the invention has been described herein withreference to particular structure, methods, and embodiments, theinvention is not intended to be limited to the particulars disclosedherein, as the invention extends to all structures, methods and usesthat are within the scope of the present invention. Unless otherwiseindicated, the structure and features of various embodiments describedherein can further be incorporated into the other embodiments describedherein as desired. Accordingly, those skilled in the art will realizethat the invention is intended to encompass all modifications andalternative arrangements included within the spirit and scope of theinvention, for instance as set forth by the appended claims.

What is claimed:
 1. An implant configured to be fixed by an anchor in anintervertebral space defined by a first vertebral body and a secondvertebral body, the implant having a top and a bottom disposed along atransversely opposite side of the implant from the top, the implantcomprising: a peripheral wall comprising a forward wall portion havingan exterior face, a rearward wall portion disposed along alongitudinally opposite side of the implant from the forward wallportion, a first side wall portion, a second side wall portion disposedalong a laterally opposite side of the implant from the first side wallportion, a top surface extending along the forward wall portion, therearward wall portion, the first side wall portion, and the second sidewall portion at the top of the implant, and a bottom surface extendingalong the forward wall portion, the rearward wall portion, the firstside wall portion, and the second side wall portion at the bottom of theimplant; a central cavity at least partially bounded by the peripheralwall, the cavity comprising an opening at the top of the implant and anopening at the bottom of the implant; and a fixation assembly comprisinga housing fixedly mountable to the peripheral wall at an opening alongthe forward wall portion, the housing comprising an upper surfaceoriented toward the top of the implant with the fixation assemblymounted to the peripheral wall, a lower surface oriented toward thebottom of the implant with the fixation assembly mounted to theperipheral wall, a front surface extending between the upper surface andthe lower surface and extending to the exterior face, and a back surfaceextending between the upper surface and the lower surface and beingdisposed along a longitudinally opposite side of the housing from thefront surface with the fixation assembly mounted to the peripheral wall,an anchor disposed in the housing and moveable between a retractedposition in which the sharpened tip of the anchor is disposed below thetop of the implant with the fixation assembly mounted to the peripheralwall, and an extended position in which a sharpened tip of the anchor isdisposed above the top of the implant with the fixation assembly mountedto the peripheral wall, and an actuator connected to the anchor anddisposed in the housing and moveable between a disengaged position inwhich the anchor is in the retracted position and an engaged positionthat places the anchor in the extended position.
 2. The implant of claim1 in which the anchor comprises a first arm angularly connected at apivot to a second arm, with the sharpened tip disposed along the firstarm and the actuator connected to the second arm by contact of a camsurface on the actuator with a cam surface disposed along the second armaway from the pivot.
 3. The implant of claim 2 in which the first armand the second arm are each disposed in a rotation plane that isperpendicular to a pivot axis passing through the pivot.
 4. The implantof claim 3 in which movement of the anchor between the retractedposition and the extended position comprises a rotation of the anchor inthe rotation plane with the pivot fixed to the housing at a hinge. 5.The implant of claim 4 in which movement of the actuator between theengaged position and the disengaged position comprises a translationhaving a longitudinal directional component.
 6. The implant of claim 4in which movement of the actuator between the engaged position thedisengaged position comprises a translation of the actuator in anaperture disposed in the housing, with the aperture having alongitudinal directional component.
 7. The implant of claim 2 in whichthe anchor is rigid.
 8. The implant of claim 1 in which the housing isfixedly mountable to a pocket in the forward wall portion of theperipheral wall.
 9. The implant of claim 8 in which the opening in theforward wall portion comprises a gap extending from the top of theimplant to the bottom of the implant, the gap separating the forwardwall portion into two sections and creating a gap in each of the topsurface and bottom surface.
 10. The implant of claim 9 in which thelower surface of the housing is disposed along the bottom of the implantadjacent to the bottom surface of the peripheral wall.
 11. The implantof claim 10 in which the upper surface of the housing is disposed alongthe top of the implant adjacent to the bottom surface of the peripheralwall.
 12. The implant of claim 1 in which the upper surface of thehousing, the lower surface of the housing, the front surface of thehousing, the back surface, and a pair of side surfaces of the housingdefine a profile substantially similar to a rectangular cuboid.
 13. Avertebral fusion device comprising: a ring-shaped implant bodycomprising upper and lower vertebral contact surfaces, an exteriorsurface extending between the upper and lower vertebral contactsurfaces, and an opening formed on the exterior surface and extendinginto the implant body; a housing removably mountable to the opening witha first end of the housing extending to the exterior surface; an anchormovable from a first anchor position in which the anchor is containedwithin the housing to a second anchor position in which a tip of theanchor extends out of the housing and away from the implant body withthe housing mounted to the opening; and an actuator having a first endcomprising a tool attachment and a second end disposed within thehousing, the anchor movable from a first actuator position thataccommodates the anchor in the first anchor position to a secondactuator position that places the anchor in the second anchor position.14. The vertebral fusion device of claim 13 in which the anchorcomprises a hinge attached to the housing.
 15. The vertebral fusiondevice of claim 14 in which movement of the anchor from the first anchorposition to the second anchor position comprises rotation of the anchorabout the hinge.
 16. The vertebral fusion device of claim 15 in whichthe tip of the anchor is disposed on a first side of the hinge and atail of the anchor is disposed on the second side of the hinge.
 17. Thevertebral fusion device of claim 16 in which the tip of the anchor issharpened and the tail of the anchor is in contact with the second endof the actuator with the actuator in the second actuator position. 18.An intervertebral fusion implant comprising: an implant body comprisingupper and lower vertebral contact surfaces, an exterior perimetersurface extending between the upper and lower vertebral contactsurfaces, and a pocket formed on the exterior surface; a housinginsertable into the pocket and detachably mountable in the pocket withan end of the housing forming an extension of the exterior surface; anactuator at least partially disposed in the housing and translatablefrom a first anchor position to a second anchor position; and an anchorat least partially disposed in the housing and comprising a first endand a second end, the first end movable in response to movement of thesecond end caused by translation of the actuator.
 19. The intervertebralfusion implant of claim 18 in which translation of the actuator resultsfrom rotation of the actuator about a central axis of the actuator. 20.The intervertebral fusion implant of claim 19 in which movement of theanchor comprises rotation of the anchor about a hinge disposed betweenthe first end and the second end.